1. FIELD OF THE INVENTION
The present invention relates to a breaker valve that is available in various types of oil hydraulic instruments or fluid systems.
2. DESCRIPTION OF THE PRIOR ART
Heretofore, in an oil hydraulic system used to raise a heavy body or in other oil hydraulic systems, in the event a portion of the conduits or rubber hoses have been damaged for any reason, or though not damaged, discharge of oil occurs at a flow rate exceeding a value preset in a breaker valve, a breaker valve would operate to shut off the oil hydraulic circuit so that the fall of a heavy body and excessive flow of oil will be prevented. In general, such a valve is called a "breaker valve", "fuse valve" or "emergency shut-off valve". Illustration is omitted because use of such a valve is a well-known fact.
However, the above-mentioned oil hydraulic systems involve the following problems. When an accident of the above-described type has occurred and after the above-mentioned emergency shut-off has operated, in some cases the damaged location is repaired after the heavy body has been lowered. Or, in an oil hydraulic system in which a plurality of oil hydraulic instruments are connected in parallel to each other and operated through a single main piping, when it is attempted to operate one of the plurality of oil hydraulic instruments while the piping for another oil hydraulic instrument is shut off at one of the locations, in some cases the pressure relationship at the breaker valve then in emergency shut-off condition would change, resulting in opening of the breaker valve. In the above-described cases, secondary accidents, such as unexpected operation of the oil hydraulic equipment to continue lifting a heavy body or unwanted discharge of fluid and the like, would occur.